Saw this on the Google Board. THought somebody might be able to get the article–it requires an account. Here is the website:
http://www.sciencemag.org/cgi/content/full/305/5687/1112
On NPR Friday there was an in depth science story which was of monumental
importance to exercise physiology. Published in Science. I haven’t read it
yet, but basically, it goes like this:Conventional thinking is that lactic acid is something bad…which degrades
muscle performance. Lactic acid forms when there is so much sugar metabolism
that the mitochondria of the cells can’t handle it. Glucose is degraded to
pyruvate to make ATP to power the muscle contraction. The pyruvate then enters
the mitochondria to go into the Krebs cycle to make still more ATP. But when
pyruvate is produced so fast that it can’t be processed by the mitochondria, it
gets converted to lactic acid, which is either stored in the muscle cell or
washed away into the blood stream. Lactic acid is a temporary storage form of
potential energy. Once the mitochondria have caught up, lactic acid can be
metabolized in the mitochondria to produce ATP to power muscles. In fact, the
preferred energy source for cardiac muscle is lactic acid, although all muscles
can “burn” it to produce ATP.But the “problem” is that lactic acid lowers the pH of the muscle cells.
Conventional wisdom is that this is bad and that the falling pH is responsible
for “poisoning” muscle contraction. So this has led to all sorts of theories
about training improving the “buffer capacity” of muscle cells (you can read
about this everywhere, including in Maglischo). And it has led to all sorts of
nutritional supplements to imrpove buffering to reduce the fall in pH, notably
sodium bicarbonate.Turns out this is all wrong. Lactic acid and the lower pH actually helps keep
the muscles working during periods of fatigue. The real culprits in causing
fatiguing muscle to stop working are potassium and phosphate. The lower pH
helps the muscle cells continue to work in the presence of the altered
potassium and phosphate concentrations.This actually makes sense, teleologically speaking. Generally, when the body
does something, it does it for a purpose. Why should humans evolve to produce
a toxin which causes muscle to shut down? It makes much more sense that lactic
acid helps the muscle fibers to compensate for ionic imbalances which occur
during extreme exercise. So, actually, the athlete would be, at least in
theory, better served by INCREASING lactate concentration, rather than
decreasing it. Yogurt is a very good source of lactic acid. I’m going to
start experimenting with “yogurt loading” right before I swim (I’m really good
at exercising with food in my stomach).The lactic acid may still be the culprit in one thing…that being the muscle
“burn.” The lactic acid, when it leaks out of the local muscle cells in high
concentrations, my activate sensory nerve receptors which are sensitive to
changes in pH. Again, it makes teleological sense for the body to have an
“early warning” system for work overload. The lactic acid “burn” is a signal
to slow down.So lactic acid is not a villain, but rather a hero. Triple threat. Storage
form of energy. Lowers pH to allow muscle cells to continue to function with
altered potassium and phosphate levels. Warns body that there is impending
overload.